OK, so a while ago I inherited this aquarium. I went to the local aquarium shop and spoke with the "experts" who work there. I chose a handful of guppies and swordtails for their ease of care. I was told that I should always have more female than male swordtails, otherwise the males will fight over the females. Well, I was checking out my fish this morning and noticed that my two females are developing swords. This means that they are, in fact, male. Do I need to run out and get a bunch of females now (and hope they stay female this time )? Or will these males live together in harmony because there are no females in the vicinity? Thanks!

Oh, the tank's plenty big enough. Three swords, three guppies and a pleco in what we think is a 35 or 40-gal aquarium.

Well, I hope it is the old female and not the late bloomer thing. I would hate to keep buying these fish only to have them change sexes on me each time so I wind up with a tank full of angry bachelors!

Some fish, usually live barers which are swordtails, platies, and guppys can infact change sex. But only female to male. If the female is not getting enough attention she will convert into a male. With guppies you tell by that little fin on the bottom of them, if it's all bunched up and straight it is a male, if it's fanned out it's a female. I actully just had one of my fav. females turn into a male . My SO breeds guppies and this happens to him a lot, he always has to go out and buy new females because he ends up with a bunch of males and only a few females.

Do be careful not to get too many males compared to the number of females. If you have too many males, especially guppies, the males will always (or so it seems) to be chasing the female. Not having a moments quiet can stress the fish out quite quickly. 50/50 is a good mix of males/females.

Also, do not assume that because you're getting a female that they will breed (if that's what you're looking for). Males and females will choose their own mates. If the ones available aren't suitable, they won't breed. They can also become quite attached. I had a male and female (breeding pair) of swords and the male died. The female committed suicide by jumping out of the tank through a one inch square opening to provide fresh air circulation. While swords are jumpers, she had never tried to jump before the male died. It was my poor luck that she jumped while I was at work and I could not save her. I've been unsuccessful since in breeding them.